JP2001017955A - Method for cleaning soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To wash soil polluted with oil or organic matter with good efficiency and economically to clean and remove the oil or organic mater in the soil and to recycle the soil. SOLUTION: In this method, one or two or more kinds of surfactants selected from the group of nonionic surfactants, anionic surfactants, and amphoteric surfactants are added to soil to wash it. In this case, the surfactants are preferably used so that the weight ratio of the nonionic surfactants and/or amphoteric surfactants to the anionic surfactants, is 1:2-1:20. As the surfactants, β-alanine amphoteric surfactants are preferably used, and amongst them, N-2-hydroxyethyl- N-2-hydroxyalkyl-β-alanines and/or alkylene oxide adducts thereof are preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soil cleaning method, and more particularly to a soil cleaning method capable of effectively cleaning soil contaminated with oil, organic matter, and the like.

[0002]

2. Description of the Related Art Contaminated soil, such as a factory site or a beach contaminated by crude oil leaked from a tanker due to a crude oil tanker stranded accident or the like, has conventionally been reclaimed or cemented. Solidification or incineration has been used for disposal, but in recent years, methods of purifying soil by removing or detoxifying contaminants in soil have become mainstream.

[0003] As a treatment method for purifying the soil,
(1) Above ground bioreduction method, (2) In situ bioreduction method, (3) Soil gas suction method, (4) Thermal desorption method, (5) Dechlorination method, (6) Chemical treatment method, ( 7)
In situ flushing, (8) soil washing, (9) solvent extraction, (10) in situ vitrification, and the like are known. Among them, the soil washing method of (8) can increase the cost-effective ratio as compared with (a) other methods,
It is a treatment method with a high treatment capacity, and is particularly economical in the case of coarse-grained soil. (B) High versatility because the same treatment system can handle both organic and inorganic pollutants. ) It has the advantages that it can be used as one method in the combined purification method, and (d) the soil after purifying the pollutants can be easily reused as compared with other methods.

[0004] Nevertheless, conventional soil washing methods require the use of solvents such as kerosene, bubbling of contaminants as in flotation or floatation, and the use of specific facilities and equipment. In fact, there are almost no treatments that take full advantage of the above-mentioned advantages of the soil cleaning method, such as those that have a huge processing cost as a whole and that have a large environmental load such as those that use kerosene. Is the current situation.

[0005] The present invention has been made in view of the above points,
An object of the present invention is to provide a method for cleaning soil that can effectively remove oil and organic substances from soil contaminated with oil and organic substances and that has a low environmental load.

[0006]

That is, the method for cleaning soil according to the present invention comprises adding one or more selected from nonionic surfactants, anionic surfactants and amphoteric surfactants to soil. It is characterized by washing the soil. In the method of the present invention, the weight ratio of the nonionic surfactant and / or amphoteric surfactant to the anionic surfactant is (nonionic surfactant + amphoteric surfactant): anionic surfactant = 1 : It is preferable to use a surfactant so as to be 1: 2 to 1:20. As a surfactant, β
-The use of alanine-type amphoteric surfactants is preferred, especially β
Among the alanine-based both-type surfactants, use of N-2-hydroxyethyl-N-2-hydroxyalkyl-β-alanine and / or an alkylene oxide adduct thereof is preferable.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, examples of nonionic surfactants include polyoxyalkylene ethers, polyoxyalkylene esters obtained by adding an alkylene oxide to alcohols, fatty acids and amines. Examples thereof include polyoxyalkyleneamines and the like, and fatty acid esters such as sorbitan fatty acid esters, monoglyceride, diglyceride, and the like, and these can be used as a mixture of two or more. Examples of the anionic surfactant include, for example, alkylbenzene sulfonic acid,
Alkyl naphthalene sulfonic acid, alkyl sulfonic acid,
Dialkyl sulfosuccinic acid, petroleum sulfonic acid, alkyl sulfuric acid, polyoxyalkylene ether sulfuric acid, polyoxyalkylene styrenated phenyl ether sulfuric acid, alkyl phosphoric acid, polyoxyalkylene alkyl ether phosphoric acid, polyoxyalkylene alkyl phenyl ether phosphoric acid, fatty acid, etc. , Sodium salts, potassium salts, amine salts and the like, sulfated oils and fats, naphthalene sulfonate formaldehyde condensates, etc., and these can be used in combination of two or more.

Further, examples of the amphoteric surfactant include an amino acid type compound, a betaine type compound, a sulfobetaine type compound, and a sulfoamino acid type compound, and these can be used as a mixture of two or more.

The above-mentioned surfactant is preferably a compound having no aromatic ring in the molecule and having an alkyl group derived from natural fats and oils because of its excellent biodegradability.

In the present invention, any one of the above-mentioned nonionic surfactants, anionic surfactants and amphoteric surfactants may be used alone, or two or more may be used in combination. When a mixture of the above is used, a nonionic surfactant and / or amphoteric surfactant and an anionic surfactant are mixed in a weight ratio of (nonionic surfactant + amphoteric surfactant): anionic surfactant It is preferable to use the agent at a ratio of 1: 2 to 1:20 because the agent has an excellent effect of washing oil and organic substances and an effect of agglomerating the soil after washing.
When preparing and using an aqueous solution of a mixture of a nonionic surfactant and / or an amphoteric surfactant and an anionic surfactant, a nonionic surfactant and / or an amphoteric surfactant are added to water and heated. After stirring and dissolving in water, an anionic surfactant is added, and the mixture is heated and stirred to dissolve, whereby an aqueous solution of the mixture can be prepared relatively easily.

In the present invention, among the amphoteric surfactants, the β-alanine-type amphoteric surfactant, which is an amino acid compound, is converted to a pH value by carbon dioxide in the air.
It is preferable to neutralize the negative ζ potential of the soil and promote the aggregation of the soil. Particularly, among the β-alanine type amphoteric surfactants, N-2-hydroxyethyl-N-2
The use of -hydroxyalkyl-β-alanines and / or their alkylene oxide adducts allows the HLB to be adjusted freely, and provides an optimal cleaning effect in response to changes in the type of soil and the type of contaminated oil. There is the advantage that it can be adjusted as required.

The N-2-hydroxyethyl-N-2-hydroxyalkyl-β-alanines are preferably those having 12 to 18 carbon atoms in the hydroxyalkyl group. 2-hydroxydecyl-β-alanine, N-2-hydroxyethyl-N
-2-hydroxydodecyl-β-alanine, N-2-hydroxyethyl-N-2-hydroxytetradecyl-β
-Alanine, N-2-hydroxyethyl-N-2-hydroxyhexadecyl-β-alanine, and lithium salts, sodium salts, magnesium salts, calcium salts thereof,
Amine salts (such as triethanolamine salts); Examples of the alkylene oxide adduct of N-2-hydroxyethyl-N-2-hydroxyalkyl-β-alanine include the above-mentioned N-2-hydroxyethyl-N-2-amine.
Compounds in which alkylene oxides such as ethylene oxide and propylene oxide are added alone or as a mixture to hydroxyalkyl-β-alanines. The added mole number of the alkylene oxide is preferably about 150 moles or less.

The oil to be treated in the method of the present invention,
The soil contaminated with organic matter includes, for example, soil on a former chemical factory site, soil on which oil and organic matter have been illegally dumped, and beach soil contaminated by crude oil leaked from a tanker due to a crude oil tanker stranded accident. ) And the like.

For carrying out the method of the present invention, for example, a method of directly spraying a cleaning liquid containing the above-mentioned surfactant at high pressure onto soil contaminated with oil or organic matter, and washing the soil on a belt conveyor, And a method of passing soil through a washing tank storing the washing liquid, stirring the soil, removing the soil from the washing tank, and draining the washing liquid.

The surfactant is preferably added so that the content in the soil when added to the soil is 0.001 to 2.5% by weight, particularly 0.05 to 0.10% by weight. It is preferable to add so that 0.001% by weight
If the amount is less than the above, a sufficient cleaning effect may not be expected. If the amount exceeds 2.5% by weight, the soil after the washing may be sticky. In the method of the present invention, a cleaning aid such as an alkanol amide, a re-contamination inhibitor such as carboxymethyl cellulose (CMC), a chelating agent,
Even if various additives such as preservatives and fungicides are mixed with the surfactant in advance and added to the soil, or before or after adding the surfactant to the soil, a re-contamination inhibitor, a chelating agent, Additives such as preservatives and fungicides may be added.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The surfactants used in the following Examples and Comparative Examples are as follows.

(1) Amphoteric surfactant a: Sodium N-2-hydroxyethyl-N-2-hydroxydodecyl-β-alanine (2) Amphoteric surfactant b: Polyoxyethylene (3 mol) -N-2 -Hydroxyethyl-N-2-hydroxydodecyl-β-alanine sodium (3) Amphoteric surfactant c: polyoxyethylene (6 mol) -N-2-hydroxyethyl-N-2-hydroxydodecyl-β-alanine sodium (4) Amphoteric surfactant d: polyoxyethylene (12 mol) -N-2-hydroxyethyl-N-2-hydroxydodecyl-β-alanine sodium (5) Amphoteric surfactant e: N- (3-dodeca Noylamidopropyl) -N, N-dimethylammonium betaine (6) Amphoteric surfactant f: 2-lauryl-N-carboxymethyl-N -Hydroxyethylimidazolinium betaine

(7) Nonionic surfactant a: polyoxyethylene (10 mol) lauryl ether

(8) Anionic surfactant a: sodium lauryl sulfate (9) Anionic surfactant b: polyoxyethylene (3 mol) sodium lauryl ether sulfate (10) Anionic surfactant c: sodium oleate

(11) Cationic surfactant a: lauryl trimethyl ammonium chloride

Examples 1 to 14 and Comparative Examples 1 and 2 As samples of contaminated soil, Putnam Silt Loam 30 g was used.
0.1 g of olive oil was added and mixed, and artificially contaminated soil contaminated was used.

A 30% by weight aqueous solution of a surfactant shown in Table 1 (50 ppm hardness water) was added to 30 g of the artificially contaminated soil.
900 g was added, and the temperature was 25 ° C. by Terg-O-Tometer.
After washing under the conditions of a washing time of 10 minutes and a rinsing time of 3 minutes, followed by natural drying, the amount of residual oil in the soil was measured and evaluated according to the following criteria. Further, a 0.1% by weight aqueous solution (50 ppm hardness water) of a surfactant was added to Putnam Silt Loam so as to have a water content of 30% by weight, and the state of aggregation after one week was evaluated according to the following criteria. Table 2 shows the results.

[0023]

[Table 1]

[0024]

[Table 2]

Detergency evaluation criterion ◎ The residual oil amount in the soil is less than 30% by weight of the added oil amount. ○ ... The residual oil amount in the soil is 30% by weight or more and less than 60% by weight of the added oil amount. Δ: The amount of residual oil in the soil is 60% by weight or more and less than 80% by weight of the added oil amount. ×: The amount of residual oil in the soil is 80% by weight or more of the amount of added oil.

Aggregation effect evaluation criteria ◎: Aggregated soil of 0.25 mm or more is 80% by weight or more. ○ · · · less than 80% by weight of aggregated soil of 0.25 mm or more,
50% by weight or more. △ · · · less than 50% by weight of aggregated soil of 0.25 mm or more,
20% by weight or more. X: Less than 20% by weight of aggregated soil of 0.25 mm or more.

[0027]

As described above, according to the method of the present invention, soil contaminated with oil and organic substances can be effectively washed. In particular, the weight ratio of the nonionic surfactant and / or amphoteric surfactant to the anionic surfactant is
(Nonionic surfactant + amphoteric surfactant): When the surfactant is used such that the anionic surfactant is 1: 2 to 1:20, the soil and the soil after washing are excellent in the effect of washing oil and organic substances. Excellent in agglomerating effect.

When a β-alanine-type amphoteric surfactant is used as a surfactant, the effect of neutralizing the negative ζ potential of the soil to promote the aggregation of the soil is obtained. Among the activators, when N-2-hydroxyethyl-N-2-hydroxyalkyl-β-alanine and / or an alkylene oxide adduct thereof is used,
Adjustment can be made to obtain an optimum cleaning effect in response to changes in the type of soil and the type of contaminated oil, so that optimum cleaning can be performed according to the type of soil and contaminated oil.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C11D 1/88 C11D 17/00 17/00 // C09K 101: 00 103: 00 F term (reference) 4D004 AA41 AB02 AB05 AC07 CA40 4H003 AD02 AD04 BA12 DA20 DB02 DC01 ED02 FA03 4H026 AA07 AB04 CB08 CC06

Claims (4)

[Claims] 1. A method for cleaning a soil, comprising adding one or more selected from a nonionic surfactant, an anionic surfactant, and an amphoteric surfactant to soil, and washing the soil. . 2. The weight ratio of the nonionic surfactant and / or amphoteric surfactant to the anionic surfactant is (nonionic surfactant + amphoteric surfactant): anionic surfactant = 1. 2. The method for cleaning soil according to claim 1, wherein the surfactant is used so as to be in a ratio of 2: 2 to 1:20. 3. A soil washing method comprising adding a β-alanine type amphoteric surfactant to soil and washing the soil. 4. The method according to claim 1, wherein the β-alanine type amphoteric surfactant is N-type.
2-hydroxyethyl-N-2-hydroxyalkyl-
The method for cleaning soil according to claim 3, which is a β-alanine and / or an alkylene oxide adduct thereof.